Sterilizing apparatus and method



2 Sheets-Sheet l il z vezztbr'x fi/mow J snscoc/r, 2] s 79315 rug H. J. BABCOCK STERILIZING APPARATUS AND ME' IHOD Flled July 31, 1933 Oct. 25, 1938.

Oct. 25, 1938. H BABCQCK A 2,134,098

STERILIZING APPARATUS AND METHOD Filed July 51, 1955 2 sheets-sheet 2 S fl/mom 18450006 Patented on. 25, 1938 2,134,098

UNITED STATES PATENT OFFICE STERILIZING APPARATUS AND METHOD Harold J. Babcock, Cleveland Heights, Ohio Application July 31, 1933, Serial No. 682,955 Claims. (01. 219 35 This invention relates to asterilizing apparatus tions inwardly and outwardly rather than inand method. More particularly, it has in View the wardly only from heating means disposed about provision of a simple and economical apparatus the circumference of the container. which is adapted for the treatment of soil to free Another object of the invention is to provide a 5 the same from harmful elements such as seed and method and apparatus for applying both heat it plant destroying fungi, bacteria, and insect life, for the purpose of destroying harmful organic and also to destroy weeds and their seeds, prelife within the soil undergoing treatment as well liminary to the use of such soil in germinating as steam to suitably condition such soil for certain seeds, propagating cuttings, and growing plants uses.

and other vegetables. Another object of the invention is to provide 10 Through such treatment it is important to sefor an electrolytic type of apparatus for direct cure uniform heat distribution over not too great heating of the soil, as well as heating through distances and to maintain the temperature range resistance elements in the manner set forth in between points sufficient to destroy harmful orthe preferred form of the invention.

.15 ganic life, while affecting very slightly or to no Other and further objects of the invention will degree the beneficial elements of organic life in appear in the course of the following description. the soil, among them the nitrogen and ammonia To the accomplishment of the foregoing and producing organisms. related ends, said invention, then, consists of the Heretofore it has been proposed to heat soil in means and method hereinafter fully described situ with the view to destroying objectionable and particularly pointed out in the claims, the 20 organic matter within the soil, particularly annexed drawings and the following description through steaming operations, but such operations setting forth in detail certain means and methods are difficult to satisfactorily control and involve embodying the invention, such disclosed means considerable wastage of the heating medium as and methods constituting, however, but several well as lack of uniformity in results produced. of various forms inwhich the principle of the 25 The present invention has for its principal obinvention may be used.

ject the provision of an apparatus and method for In said annexed drawings: sterilizing soil so that dependable results may be Figure l is a top plan view of an apparatus obtained, and propagation of plant life carried embodying the principles of the invention;

on with the assurance that no harmful organic Figure 2 is a side elevation of the apparatus 30 matter is present in the soil preliminary to its shown in Figure 1; being used for the special work in hand. Figure 3 is a central vertical sectional view,

Another object of the invention is to provide taken along the line 3-3, shown in Figure 1, looka very large extent of heat radiating surface ing in the direction of the arrows; through the use of a very long continuous elec- Figure 4 is a central transverse sectional view, 35 trical resistance element, thus providing a relataken along the line 4-4, shown in Figure 2,

tively low temperature differential between such looking in the direction of the arrows;

heating element and the actual temperature at- Figure 5 is a diagrammatic view, partly in sectained in the soil, and avoiding high temperatures tion, showing an apparatus provided with an in- 40 harmful to beneficent organisms. dependent thermostatic control; 40

A further object of the invention is to provide Figure 6 is a diagrammatic view of the thermoan inexpensive readily portable apparatus which static control and series plug shown in Figure 5; will distribute the heat throughout the soil under- Figure 7 is a diagrammatic view of the heating going treatment in a substantially uniform element and thermostat embodied in the structure amount throughout the full extent of the apparashown in Figure 5; and 45 tus. Figure 8 is a central vertical sectional view of Another object of the invention is to provide a an electrolytic type of apparatus.

method of sub-dividing the soil undergoing treat- As is clearly shown in the drawings, the prement in such manner that portions of the soil ferred form of apparatus comprises a container l will act as a heat retaining element with refpreferably of cylindrical form, and in the speci- 50 erence to the remaining portion of the soil, and men illustrated comprising a sixty-five gallon that all portions of the soil undergoing treatment drum adapted to hold approximately nine cubic will receive approximately uniform quantities of feet of soil and being approximately two feet in heat, and with the heat traveling from a source diameter and three feet high, although the dimenpositioned at an intermediate point in two direcsions set forth are purely illustrative and by no 55 means essential to the successful operation of the invention.

The container just described is formed as a double walled receptacle, there being provided an outer shell 2 also preferably formed of sheet metal and of sufficiently larger diameter than the container l to permit the interposition between the same of a heat insulating filling 3, preferably of rock W001 or some equivalent heat insulating material.

Within the receptacle so formed, a heating element 4, preferably in the form of a hollow cylindrical structure open at each end, is provided, such element carrying suitably insulated electrical resistance elements 5, 6, adapted to provide the desired quantity of heat, as will be hereinafter explained. The hollow cylindrical structure is preferably supported at its lower end by means of a plurality of standards 1, securedto a supporting circumferential band 8 secured about the lower portion of the element, and such standards having outwardly turned lower ends 9 fastened to the base H of the container. The upper portion of the hollow cylindrical element is likewise provided with a supporting band 2, to which at intervals a bracket arm i3 is secured to maintain the same in spaced relation to the adjacent inner wall surface of the receptacle.

The hollow cylindrical element 4 is preferably formed of a pair of sheet metal'plates, one of slightly smaller diameter than the other, telescoped within each other so as to provide an intermediate space M between the walls to accommodate the resistance elements 5, 6, which are preferably non-inductively woundin paired circumferential windings about the inner shell and fitted closely within the outer shell. The ends of the sheet metal shells forming the hollow cylindrical element may be crimped upon each other or secured or locked to each other in any suitable manner, and bands with suitable tensioning elements may be used to bring the outer shell into close relation to the inner shell and its superimposed coils of wire.

The electrical resistance elements 5 and 6 preferably are formed of a nichrome or like resistance element suitably encased and insulated in lead or steel sheathed cable or the like. Such insulation may be formed of several layers of impregnated fabric having Glyptol or some insulating lacquer thereover and having an outer sheath or cover preferably of lead or lead alloy. The wire, as is clearly shown in Figure 3 is wound about the inner shell of the hollow cylindrical element from a point approximately centrally of said element in helical form toward the top of said element, the turns of wire being more closely spaced adjacent the top so as to provide increased heating effect at such point. Likewise the wire is wound in a helical coil toward the lower end of the hollow cylindrical element, the wires likewise being more closely spaced adjacent the lower portion, and preferably in a greater degree of closeness than adjacent the top in view of the fact that the lower portion of the container would normally receive less heat than the upper portion and therefore would require a greater proportion of heat transferring means at such point.

The terminals of the two sections of electrical resistance elements 5 and t are carried through conduit sections I5 and connecting boxes 5 positioned at one side of the inner wall of the hollow cylindrical element and such conduit is carried by means of cross conduits I1 and connecting box l8 to a terminal plug l9 providing a suitable connection with the power line. The power may be carried through a flexible cable (not shown) and a thermostatic element 20 may be associated with the terminal I9 or placed elsewhere in the apparatus.

The receptacle may be provided with a cover 2| having a circumferential depression 22 so as to provide a snug fit for the apparatus and to permit the natural moisture of the soil to form a certain degree of steam pressure within the container. If desired, suitable aperture; with or without valves may be provided in the cover to limit the steam pressure to any amount required for the particular conditioning of the soil.

The procedure with an apparatus of the character described comprises the filling of the receptacle with the soil which it is desired to sterilize, such soil being placed about the periphery of the hollow cylindrical element as well as within the same and the container completely filled to its upper portion. The current is then turned on and the contents of the container provided with heat of something above 140 Fahrenheit, and ranging preferably from 140 to 220 Fahrenheit, under which conditions the apparatus described is adapted to thoroughly sterilize the soil placed within the same. The period of sterilization may vary with the moisture content andother characteristics of the soil, but if soil of average condition is treated, a continuous heating of the same for a period of approximately eight hours is adequate to completely destroy all objectionable organic matter within the same.

Where vapor treatment of the soil is desired, a

gas-tight cover is required and with soil having a moisture content of approximately seventeen per cent, a satisfactory quantity of steam will be generated to thoroughly condition the soil as to friability as well as to a proper degreeof sterilization. I In place of winding the heating elements about the hollow cylindrical member in the form of a helix or a pair of helices, the same may be secured to one of the walls of a shell forming the hollow cylindrical element, by winding the-same i sinusoidal loops about the projections extending inwardly from such container walls. In such event, it is preferableto provide somewhat longer widely spaced loops adjacent the upper portion of the hollow cylindrical element and shorter more closely spaced loops adjacent the lower portion thereof so as to provide more heating surface adjacent the lower portion of the container than adjacent its upper portion.

Through the apparatus above described, soil for use in growing plants in pots, flats, greenhouse benches, or garden plots, may be provided in the quantities required by successively treating portions thereof as above outlined.

In the structure shown in Figures 1 to 4 in clusive, a thermostatic element is shown as disposed within the container adjacent one side thereof, such thermostat being a permanent part of the apparatus. In view of the fact that it may be found desirable to supply containers without thermostatic control, and to provide independent thermostatic elements to be used whenevermore refined control of the apparatus is required for certain special soil treatment operations, the apparatus shown in Figures 5, 6 and '7 is provided. The container 3| is substantially similar to that heretofore described, having a cylindrical element 32 within the same carrying the resistance element 33, which as shown in Figure 7, may be non-inductively wound. The conducting elements 34 forming part of the electric circuit connecting with the heating elements are carried through a connecting box 35 and a cross conduit 35 to a box 31 having a flexible cable 38 extending therefrom and carrying a terminal plug 39.

When the device is used without a thermostatic element, the plug 39 is adapted to be fitted into any suitable outlet box connected with a source of power. When it is desired to use a thermostatic element in connection with the apparatus, the plug 39 is fitted into a series junction box 4| connecting with the contacts 42, 43. The thermostatic control element is housed in a casing 44. The bulb 45 of the thermostat is connected by a conventional tube '46 with a closed metal bellows 41 at one end, the other end of the bellows having a bar 48 adapted to bear against a movable switch member 49, pivotally supported at one side of the casing upon a pivot pin 5|, and having an adjusting bar 52 to shift the same upon the casing wall to secure any desired degree of temperature control. The free end of the switch member carries the contact 53 cooperating with a fixed contact 54. The conducting member 55 from the movable switch member is connected with a contact 56 within the junction box 4|, and the conductor 57 from the fixed terminal is connected with a contact 58 within the junction box through a plug 59 carrying said conductors. The current is supplied to the junction box through the conductors GI, 62, which are provided with a terminal plug 63 adapted to be engaged in the side of the junction box. Thus the junction box serves to connect the thermostatic circuit with the heating unit circuit in series, and it is unnecessary to change the Wiring of the apparatus which is ordinarily equipped with a single terminal for plugging into an outlet box of a source of current supply with a permanent attachment for a thermostatic control element. It is obvious that the thermostatic element may be removed and a suitable conducting plug inserted in place of the plug 59 of the thermostatic control to complete the circuit for the apparatus independently of the thermostat, should the convenience of operation make such arrangement desirable.

The method embodied in the invention comprises the steps of providing electrical heating means in the form 'of a hollow cylindrical element, and spacing soil to be treated about the circumference thereof as well as within the interior thereof and beyond each of the ends thereof, to such extent that the degree of heat imparted to the adjacent soil by such heating element will be substantially uniform throughout the extent of such interposed and surrounding soil.

The method also includes the proportioning of the extent of heating element within a container, particularly a container open at one end, in such manner that the amount of heat transmitted through the confined lower portion thereof is transmitted by a greater extent of heat transferring elements, and adjacent the upper portion by a lesser extent of heat transferring elements, so that substantially uniform heat conditions will prevail throughout the soil area referred to. Thus, the masses of soil are proportioned and distributed throughout the apparatus, as well as intermediate the heating elements, so that maximum efiiciency of the apparatus is secured and substantially uniform temperatures are maintained.

Where a valve is utilized in the cover to combine steam treatment with the heat treatment, it

is preferable to use a valve permitting a pressure range of from one to five pounds.

In place of utilizing electrical resistance elements to transfer heat to the soil, the current conducting container H, as shown in Figure 8, may be formed with a central electrode 12 integral with the bottom and side walls and serving with them as the negative terminal of an electrical circuit [3. Insulated from the terminal elements just described, a positive electrode is provided, preferably in the form of a hollow cylindrical current conducting shell 14 surrounding the central electrode and supported upon insulating standards 15 in spaced relation to the bottom, and insulating spacing members 16 at the sides. The other end of the circuit is connected with the shell 14 preferably through an aperture in one of the insulating supports 16. When the circuit is closed, the currents of electricity will flow from positive electrode I2 in each direction toward the outer walls of the container and toward the central negative electrode just described. In this manner with the proper moisture content of the soil, a suitable degree of heating action may be applied to the intermediate soil as well as the electrolytic effects due to current conduction through the moist soil, and soil conditioning can be brought about in such manner. The quantity of current required and the rate of sterilization brought about will conform to the particular requirements of the work in hand including the character of the soil treated and the time permitted for the various operations.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the structure herein disclosed, provided the means and steps stated by any of the following claims, or the equivalent of such stated means and steps, be employed.

I therefore particularly point out and distinctly claim as my invention:

1, A method of sterilizing soil which comprises the steps of providing a hollow cylindrical noninductive electrical heating element having higher effectiveness for heating adjacent its lower portion than its upper portion, surrounding the same with a hollow cylindrical layer of soil of predetermined thickness adapted to serve as an insulating heat confining element as well as material for heat treatment, placing, within the center of such element and its protective layer, a core of additional soil of slightly less total mass than the hollow layer of soil, and thereafter applying heat through such cylindrical hollow heating element to effect uniform distribution of heat throughout the mass of soil referred to.

2. An apparatus of the character described,

having in combination a closed heat insulated container of substantially cylindrical form having side and bottom Walls, a hollow cylindrical electrical heating element engaged within said container in spaced relation to the side and bottom walls thereof, and providing two substantially concentrically arranged areas, centrally of said container, to receive substantially separate outer and inner masses of the material to be treated, said outer area being of somewhat greater capacity than said inner area, and the mass of material in said outer area serving to heat insulate the mass of material in said inner area and means for conducting current to said hollow cylindrical element.

3. An apparatus of the character described, having in combination a closed heat insulated container of substantially cylindrical form having side and bottom walls, a hollow cylindrical electrical heating element engaged within said container in spaced relation to the side and bottom Walls thereof, and providing two substantially concentrically arranged areas, centrally of said container, to receive substantially separate outer and inner masses of the material to be treated, said outer area being of somewhat greater capacity than said inner area, and the mass of material in said outer area serving to heat insulate the mass of material in said inner area and means for conducting current to said hollow cylindrical element and controlling the rate of current supply in proportion to the heat required.

4. An apparatus of the character described, having in combination a closed heat insulated container of substantially cylindrical form having side and bottom walls, a hollow cylindrical electrical heating element engaged within said container in spaced relation to the side and bottom walls thereof, and. providing two substantially concentrically arranged areas, centrally of said container, to receive substantially separate outer and inner masses of the material to be treated, said outer area being of somewhat greater capacity than said inner area, and the mass of material in said outer area serving to heat insulate the mass of material in said inner area, means for conducting current to said hollow cylindrical element, and a cover substantially sealing the top of said container.

5. An apparatus of the character described, having in combination a closed heat insulated container of substantially cylindrical form having heat insulated side and bottom walls, a hollow cylindrical electrical non-inductively wound heating element engaged within said container in spaced relation to the side and bottom walls thereof, the diameter of said hollow cylindrical heating element being so related to the diameter of the container within which the same is disposed as to provide a larger cubic capacity of the container intermediate said cylindrical element and the walls of said container than within said cylindrical element, but with a less distance between said element and the walls of said container than from the center of such container to the walls of said cylindrical heating element, and means for conducting current to said hollow cylindrical element.

HAROLD J. BABCOCK. 

